Shaped charge and method of manufacture therefor



March 11, 1969 G. B. CHRISTOPHER 3,431,850

SHAPED CHARGE AND METHOD OF MANUFACTURE THEREFOR Filed July 15. 1967 Sheet INVENTOR GLENN B. CHRlSTOPHER all MM,

March 11, 1969 3. 8. CHRISTOPHER 3, 3 ,850

SHAPED CHARGE AND METHOD OF MANUFACTURE THEREFOR Filed July 13, 1967 Sheet FIG] GLENN B. CHRISTOPHER BY m,

FIG. 8

IQBN United States Patent 9 Claims ABSTRACT OF THE DISCLOSURE A liner for a shaped charge which includes a conical, peripherally extending, main wall of uniform thickness converging axially inwardly from an open outer end. A closed inner apex portion integral with the main wall is of relatively thinner, varying wall thickness. The main wall includes two slots which extend axially of the wall to divide it into two wall parts. The slots may be spaced peripherally by less than half a circumference to cause the wall to be unequal or alternatively the slots may be of unequal length.

A method for manufacturing the shaped liner which includes cutting an integral, sheet metal blank in the form of two oppositely directed intersecting, arcuate segments disposed about a common diameter and press forming the blank between conoidal mating press members.

Background of invention This invention relates to a liner for shaped explosive charge and to a method for making the liner.

The use of so-called shaped charges in performing explosive operations requiring fiocussed, highly localized, blast effects is well known. One common form of shaped charge unit includes a hollow housing adapted to receive a cone-shaped, uniformly thick, sheet metal liner which has its exterior surfaces in contact with a body of explosive positioned between the liner and the interior of the housing.

Charge liners of this simple type, though widely used, may prove unsatisfactory for a number of reasons. For example it is sometimes the situation that the liner projects so far into the interior of the housing that the amount of explosive positioned between the apex of the liner and an adjacent end wall of the housing is substantially less than the average amount of explosive per unit area distributed over the remainder of the liner. In such situations the blast effect may be seriously reduced and it is thought that this may arise because destruction of the apex of the liner may occur relatively less swiftly than destruction of the walls of the liner during charge detonation with a substantial and deleterious effect upon the focussing and development of the blast efiect.

Another problem commonly encountered is that in using a shaped charge to produce a hole in a workpiece (for example, a hole in a well wall), the hole produced by the charge may frequently be plugged by some of the metal formerly comprising the charge liner. It is believed that one reason for this phenomenon may be that explosion of the charge proceeds so rapidly as to be completed before all the charge liner has been vaporized, with the result that a melted residuum of the charge liner follows the explosive gases through the hole produced to produce plugging thereof.

Another disadvantage may arise if it is desired to pro- 3,431,850 Patented Mar. 11, 1969 duce holes of differing diameter utilizing housings and charges of standardized dimension as may frequently be required. In this event, the use of uniformly configured charge liners provides no opportunity for varying the diameter of the various holes produced.

Additionally, it has been found that in using charge liners of the type described, it is important to provide side wall portions which are of uniform thickness in order to gain the most effective charge development. One charge liner previously provided for this purpose utilizes a centrally notched, hemispherical blank which is rolled to provide a metal cone of uniform thickness having a truncated open apex. However, such a liner suffers from the serious disadvantage that some of the shaped charge material, which is frequently granular in nature, may escape through the open aperture with possible safety hazards and loss of charge performance.

Summary of invention It is therefore a general object of the invention to provide a liner for a shaped charge designed to obviate or minimize problems of the type previously described.

It is a particular object of the invention to provide a liner for shaped charge intended to provide enhanced blast development, even when used in a housing so configured as to reduce the amount of explosive available adjacent the apex of the liner relative to that available adjacent other portions thereof.

It is another particular object to provide a liner for a shaped charge in which plugging of the hole in the work by the melted residuum of the liner is effectively minimized.

It is a further object to provide a liner for a shaped charge adapted to control the size of the hole produced by a shaped charge of predetermined magnitude.

It is another object to provide a liner for a shaped charge of the type adapted for optimum blast development, which obviates the possibility that portions of the explosive may escape through apertured portions of the liner.

It is a final object of the invention to provide a method for making a charge liner to accomplish the foregoing objects which utilizes a simple press forming step rather than the relatively less simple rolling or spinning steps frequently used heretofore.

In a preferred embodiment, the invention includes a particular charge liner in combination with a shaped charge housing. This housing is of the type including a chamber and a peripheral edge defining a circular opening communicating with the chamber. The charge liner includes a conical, peripherally extending main wall of uniform thickness having an outer peripheral rim secured to the peripheral edge of the housing, with the wall extending into the chamber. Integral with the main wall is a closed, inner, apex portion of relatively less thickness than the main wall. Explosive is positioned between the liner and interior portion of the housing defining the chamber. The amount of explosive per unit liner area between the apex portion of the liner and the adjacent interior portions of the housing is less than the average amount of explosive per unit liner area between the main wall of the liner and the housing. In this situation the relatively reduced thickness of the apex tends to ensure that the destruction of the apex portion does not lag behind the remainder of the liner during charge detonation.

The main wall portion includes at least two axially extending slots spaced peripherally of the main wall portion and dividing the latter into at least two wall parts. In a first alternative embodiment of the invention the slots are spaced peripherally by less than half a circumference thus causing the wall parts to be of unequal size. Provision of such unequal wall portions has been found to cause the melted residuum of the liner subsequent to explosion, to follow the explosive gases in an oblique path towards the hole produced so that plugging of the hole is avoided.

In a second alternative embodiment of the invention, the slots in the wall portion may be of unequal length to provide another asymmetric distribution of the wall parts.

In further embodiment of the invention, the apex portion may be configured to include at least one flat face generally transverse of the liner axis, as such variation of configuration has been found to provide a measure of control over the diameter of the hole produced by an explosive charge of particular magnitude.

The drawings One preferred embodiment of the invention is illustrated in the following drawings in which:

FIGURE 1 is a part sectional, perspective view of a charge liner according to the preferred embodiment of the invention, shown positioned within a shaped charge housing;

FIGURE 2 is a cross sectional side view of the charge liner shown in FIGURE 1 taken along lines 22 therein;

FIGURE 3 is a plan view of a blank utilized in manufacturing the charge liner shown in FIGURE 1;

FIGURE 4 is a part sectional, perspective view of a press forming die and tool pair used in the method of forming the charge liner, shown in an initial step of the method;

FIGURE 5 is a part sectional, perspective view of the die and tool pair shown in FIGURE 4, shown in an intermediate step of the method;

FIGURE 6 is a part sectional, perspective view of the die and tool pair shown in FIGURE 4, shown in a final step of the method;

FIGURE 7 is a perspective view of a first alternative embodiment of the charge liner;

FIGURE 8 is a perspective view of a secnod alternative embodiment of the charge liner;

FIGURE 9 is a perspective view on an enlarged scale of an apex portion of the charge liner shown in FIGURE 1; and

FIGURE 10 is a perspective view on an enlarged scale of an apex portion of a third alternative embodiment of the charge liner.

Detailed description Referring to FIGURE 1 of the drawings, the preferred embodiment of the invention there shown includes a conoidal, thin-walled, metal charge liner 2 positioned within a housing 4. The housing 4 is of a conventional type including an interior chamber 6 defined by a cylindrical interior wall 8 intersecting a closed, radial inner end wall 10. The chamber 6 includes an open forward end 12 defined by a forward peripheral edge 14. A forward end cap 16 is press fitted onto the housing over the open end 12 to retain the charge liner 2 within the housing. A booster 17 for initiating detonation of a body of explosive 18 positioned in the housing, is provided. The booster 17 does not however in itself contribute materially to the blast effect and is not considered to be included in the explosive as the term is generally used hereinafter. Although one particular type of conventional shaped charge housing has been described, it will be appreciated that other forms of housing familiarly used in shaped charge applications may be provided.

The liner 2 includes a conical, rearwardly converging, peripherally extending main Wall 22 which, in order to provide the most effective development of the charge on detonation, is of uniform wall thickness Integral with the main wall 22 is a closed apex portion 24 spaced forwardly from the adjacent end wall 10 of the housing The liner 2 in the preferred embodiment is formed from copper, though other suitable metals, metal alloys and other materials may be utilized if it should be desired The space between the liner 2 and the adjacent interior portion of the housing 4 is filled with the explosive 18 The extent to which the liner 2 projects into the chamber 6 is such that the average amount of explosive per unit liner area between the apex 24 and the most closely adjacent interior portions of the housing measured in directions perpendicular to the surface of the apex portion is relatively smaller than the average amount of explosive per unit area of the liner between the main wall portion 22 and the most closely adjacent interior portions of the housing measured in directions perpendicular to the main wall. In order therefore to ensure that destruction of the center of the liner relative to the remainder of the liner during explosion should not be delayed due to the lesser amount of explosive per unit area available axially adjacent the apex, the apex portion 24 is provided with a thinner wall thickness than that of the main wall 22 (see also FIGURE 2). In this manner, degradation of the blast due to late destruction of the conical central portion of the liner is advantageously minimized.

Another advantage provided by the relatively reduced wall thickness of the apex portion 24 is that the greater resilience and flexibility are provided at the apex of the liner so as to tend to reduce undue compression and packing of the explosive in the area of the liner apex. Additionally, the closed apex 24 prevents loss of explosive during storage.

This desirable configuration of the liner 2 is achieved by cutting a blank 28 from sheet metal into the form shown in FIGUURE 3. The blank 28 is defined by two oppositely directed, mutually intersecting arcuate portions 30a and 30b of equal, but not concentric, radius disposed about a common axis. The portions 30a and 30b are defined by curved peripheral edges 32a and 32b respectively, each of which is bounded by two angularly spaced radial edges 34a and 34b respectively. The edges 34a and 34b are subsequently moved into closely spaced relation by press forming the blank 28 in a conventional press couple (FIGURES 4-6). The press couple includes a conventional conoidally recessed female die 35 and a conoidal male press forming tool 36 adapted to matingly engage the die. In an initial step the blank 28 is supported on the die 36 as shown in FIGURE 4 with the tool 36 on an opposite side of the blank from the die. In an intermediate step shown in FIGURE 5 the tool 36 is pressed into the die to deform the blank 28 into a conoidal shape disposed between the tool and the die. In a final step the tool (FIGURE 6) is forced even further into the die to complete shaping of the walls and to cause drawing down of the apex portion with local thinning of the wall thickness of the liner in the apex region. The three steps are run continuously together during the press forming process. The adjacent edges 34a and 34b define axially extending slots 37 (FIGURE 1) in the wall portion 22 of the liner 2.

The liner 2 is then removed from the die. One of the previously mentioned charge housings 4 is filled to a substantial extent with explosive 18. The liner 2 is then pressed, apex first, into the housing 4 under considerable pressure to pack the explosive firmly between the exterior of the liner 2 and the adjacent interior wall portions of the housing 4. The cap 16 is press fitted to the housing 4 to retain the liner and explosive in position.

Another embodiment of the invention, particularly intended to obviate the problem of plugging of a hole produced in the workpiece by the melted residuum of the liner, is shown in FIGURE 7. In this embodiment the main wall 22 is provided with two peripherally spaced slots 38a and 38b extending axially outwardly from a point spaced from the apex 24 to the peripheral edge of the liner. The slots 38a and 38b are spaced peripherally by less than half a circumference so that the slots divide the liner 2 into circumferentially unequal wall parts 39 and 40. It has been found that such unequal distribution of the liner wall relative to the axis thereof causes a residuum of the liner produced by melting during detonation of the charge, to follow the explosive charge gases in an oblique path towards a hole produced by the gases in the workpiece. In following such an oblique path, the melted residuum usually strike the workpiece adjacent the rim of the hole rather than following the gases centrally into the hole, with the result that undesirable plugging of the hole is minimized or entirely eliminated.

Although the reasons for this effect is not entirely understood, it is believed that in the detonation of the charge, some portions of the liner are usually disintegrated in advance of other portions of the liner, and that the surviving portions become melted during the explosion and are sucked through behind the advancing explosive gases. By providing unequal masses of melted metal on either side of the path of the gases, the metal is believed to be induced to follow an oblique path with the observed desirable result. It will be appreciated that the foregoing explanation is presented merely as one hypothesis which may be helpful in understanding the observed phenomenon, and that the invention is not to be limited in the light of this explanation if other more persuasive explanations for the observed effect should later be developed.

It has additionally been found that a similar result may also be achieved by providing peripherally spaced slots 41a and 41b which are of unequal length, as shown in FIGURE 8.

A charge liner provided with asymmetrically distributed slots may be produced by the press forming method previously discussed for the first embodiment of the invention, with the modification that the arcuate portions 30a and 30b should be of unequal angular extent so that on press forming the slots do not align themselves along a diameter of the cone. Alternatively (or additionally) asymmetrically disposed slots may be cut in the blank 28 prior to press forming thereof.

The apex portion 24 (shown in FIGU-RES 1 and 3 and in more detail in FIGURE 6) includes a smoothly rounded nose blending tangentially with the sidewalls of the cone. However, it has been found that by providing apex portions 24 of a differing configuration the diameter of the holes produced in a workpiece may be varied. For example, a flat-ended nose (shown in FIGURE 10), extending radially of the axis of the liner enables the diameter of the hole produced by a particular explosive charge of predetermined magnitude to be increased relative to that provided using the liner shown in FIGURE 3. By therefore providing charge liners 2 having dilferingly configured apex portions 24, it is thus possible to effect a significant measure of control over the diameter of the hole produced in a workpiece by a fixed amount of explosive contained within a housing 4 of standardized dimension. It will be appreciated that in this manner a widened range of shaped charge applications may be undertaken utilizing a charge and charge housing of standardized type.

In following the present invention, a liner for a shaped charge having significant advantages is provided.

In particular, the provision of a charge liner having an apex portion which is relatively thinner than the remainder of the liner ensures that any reduced distribution of explosive within the housing immediately adjacent the liner apex does not impair effective development of the explosive force.

Also, the flexible and resilient qualities of the apex portion arising from its relative thinness ensure that undue compression of the charge particles in storage is minimized or reduced.

Additionally, the provision of a closed apex on a main wall of uniform thickness prevents any inadvertent loss of explosive.

Further advantages are provided by the offset slots in the first alternative embodiment of the invention and by the slots of unequal length in the second alternative embodiment which it has been found reduce the possibility that a melted residuum of the charge liner will follow the explosive gases into the hole caused thereby, to effect plugging of the hole.

Other advantages are provided by the varyingly configured apex portions of the charge liners which enable a range of differing hole diameters to be produced, in utilizing a charge and charge housing of standardized type.

I claim:

1. In combination:

a shaped charge housing including interior portions defining a chamber and a peripheral edge defining a circular opening in said housing communicating with said chamber;

a charge liner, said charge liner including:

a conical, peripherally extending main wall of uniform thickness, said main wall having an outer peripheral rim secured to said peripheral edge of said housing, said wall extending inwardly of said chamber;

a closed inner apex portion integral with said wall, said apex portion of said liner being of relatively thinner wall thickness than said main wall of said liner; and

at least two slots in said main wall spaced from said apex portion and extending axially outwardly therefrom, said slots defining said wall into at least two wall parts; and

a body of explosive poistioned between said liner and the interior portions of said housing defining said chamber, with the average volume of explosive per unit area of said liner between said apex portion and the most closely adjacent interior portions of said housing measured in directions perpendicular to the surface of said apex portion being less than the average volume of explosive per unit area of said liner between said main wall and the most closely adjacent interior portions of said housing measured in directions perpendicular to said main wall.

2. A shaped charge as defined in claim 1 wherein said main wall parts are of unequal area.

3. A shaped charge as defined in claim 1 wherein said slots are of unequal axial extent.

4. A shaped charge as defined in claim 1 wherein said apex portion includes a smoothly rounded nose blending tangentially with said main wall of said liner.

5. A liner for a shaped charge comprising:

a conical, peripherally extending, main wall of uniform thickness, said main wall converging axially inwardly from an outer end thereof;

a closed, inner, apex portion integral with said main wall, said apex portion being of relatively less wall thickness than said main wall; and

at least two slots in said main wall commencing at points adjacent said apex portion and extending axially outwardly therefrom, said slots dividing said main wall into at least two wall parts of susbtantially unequal area.

6. A liner for a shaped charge as defined in claim 5 wherein said wall parts are of substantially unequal circumferential extent.

7. A liner as defined in claim 5 wherein said slots are of substantially unequal axial extent.

8. A liner for a shaped charge comprising:

generally converging wall means extending about and surrounding an axis; and

at least two axially extending slots, said slots being spaced peripherally of said body to define major and 7 8 minor wall parts of substantially unequal circum- References Cited ferelmal extent" UNITED STATES PATENTS 9. A llner for a shaped charge compnsmg: generally converging wall means extending about and 3,217,650 11/1965 Paul et 102-24 surrounding an axis. and 3,251,300 5/1966 Reyne 102-24 5 3,268,016 8/1966 Bell l02-24 at least two axially extending slots spaced peripherally gi ii igggz bemg Substamlany unequal VERLIN R. PENDEGRASS, Primary Examiner.

Disclaimer and Dedication 3,431,850.Glenn B. Christopher, Arlington, Tex. SHAPED CHARGE AND METHOD OF MANUFACTURE THEREOF. Patent dated Mar. 11, 1969. Disclaimer and Dedication filed Sept. 26, 1983, by the assignee, Jet Research Center, Inc.

Hereby disclaims and dedicates to the Public the remaining term of said patent.

[Oflicial Gazette November 22, 1983.] 

